This invention relates to a diaphragm operated air flow control valve of the type typically used in the dust collector industry. The valve of the invention will be suitable for use in that industry, but it is to be understood that the valve of the invention can be used in other applications as well.
Air flow control valves used in the dust collection industry have a series of reasonably specific design constraints which they must meet in order to operate effectively. For example, typically the valves have inlets and outlets arranged at 90xc2x0 to each other, the valves are typically electronically controlled, and the supply and outlet pipes which lead towards and away from the valve are typically either 20 mm, 25 mm or 45 mm in diameter.
Typically these valves have a valve closure member mounted to a diaphragm and by controlling the pressure on opposite sides of the diaphragm the valve can either be opened or closed. The pressurised air supply provides the necessary pressure for controlling the valve and a bleed arrangement is provided for supplying air under pressure to opposite sides of the diaphragm.
Since these aspects of the valves are well-known, they need not be described in this document in any great detail.
There are important performance characteristics which such valves must meet in order to be competitive in the industry. For example, the valves must open rapidly and there must be a minimum pressure drop across the valve when the valve is open. In addition, the valves should be relatively easy to manufacture, assemble and install, and maintenance of the valves should be possible without removing the valve body from the equipment onto which is has been installed.
According to one aspect of the invention there is provided an air flow control valve including:
a valve body having an internal cavity and an inlet and outlet in flow communication with the internal cavity, the axes of the inlet and outlet being aligned at substantially 90xc2x0 to each other;
a valve seat located within the cavity and co-axially aligned with the outlet, the valve seat being located on the distil end of an upstanding tubular pedestal which is formed around the outlet;
the internal cavity being configured so as to define an annular space around the pedestal with which the inlet is in flow communication,
flexible generally planar diaphragm mounted above the valve seat, the diaphragm supporting a valve closure member which is adapted to engage the valve seat to close the valve;
valve control means for causing the diaphragm to move towards and away from the valve seat to close and open the valve respectively; and
the valve being characterised in that, with the valve oriented with the inlet axis horizontal and the outlet facing downwards, the valve seat is located at an elevation at or below the upper most edge of the inlet, and the diaphragm is located at an elevation above the upper most edge of the inlet.
Preferably the upper most edge of the valve seat is located a distance which is approximately one third the diameter of the inlet above the centre line of the inlet.
Preferably the valve body has a bowl portion in which the inlet and outlet are located, and a cap portion in which the valve control means is located, the cap portion having screw threads thereon adapted to engage with screw threads on the bowl portion, the diaphragm being captively held in position between the cap portion and the bowl portion when the cap portion is operatively screwed onto the bowl portion. The screw threads on the bowl portion are preferably of female configuration, and the threads on the cap portion are preferably of male configuration.
A further feature of the invention provides for the cross sectional area of the annular space or bowl area relative to the area of the valve seat to be in the range of 2.5:1 to 4.5:1, and preferably in the range of 3.2:1 to 3.6:1.
The internal diameter of the valve seat is preferably larger than the internal diameter of the outlet, and the inner wall of the tubular pedestal preferably tapers convergently from the valve seat towards the outlet.
The inlet and outlet can have any suitable connection arrangement for connecting air flow conduits to the valve. In one arrangement the inlet and outlet both have an internally threaded socket adapted to each receive a respective externally threaded tubular conduit.
The diaphragm can have a bleed hole (such as bleed hole 26 of FIGS. 1 and 7A) therethrough adapted to feed pressurised air from the annular space into the area above the diaphragm. Optionally the diaphragm can be spring-loaded into engagement with the valve seat. If desired a combination of a bleed hole and spring bias can be utilised.
The present invention also provides a valve body and cover, said valve body including a threaded portion to engage a mating threaded portion on said cover, said body and said cover having respective engagement members which are adapted to engage each other in use, said members being positioned so that said cover, when threaded onto said body, will rotate a necessary number of turns to secure said cover to said body to a predetermined torque, indicated by said engagement members engaging each other preventing any further tightening, said engagement members not engaging or contacting until said predetermined torque is reached.
Preferably it takes 1xc2xd turns to secure said cover from first engagement of the threads of said cover and body until engagement of the respective engagement members.
The engagement members can be located outside of a circumference of said cover, or alternatively located within a circumference of said cover. Preferably said cover and said body include a releasable securing means so that said cover cannot be unsecured from said body until said releasable securing means has been released.
Preferably said cover body each have an aperture therein so that once said engagement members are engaged, said apertures are aligned so as to receive a locking means. Preferably said locking means is any one of: a pin; a plastic pin; a cable tie or a retractable pin.
Alternatively said body can include a system pressure activated pawl, with said cover having a recess or aperture, whereby when said valve is pressurised the pawl moves into said recess thereby locking the cover and body together until depressurised.
Preferably the threaded portion of one or both of said cover and said body includes at least one groove extending generally laterally relative to the thread direction, said at least one groove permitting the exhaust of gas in said valve body once a seal between said cover and said body is broken.
The engagement members can be protruding bosses, lugs, faces, pins, or any appropriate formation, or combinations of these, which can extend laterally or axially relative to the valve body and or cover.
An operator to open and close a control valve having:
a body member which is separate from said control valve but is connectable thereto, said body member having a first side with connection means for connection to said control valve and a second side to engage a valve member;
said body member including a passage communicating from said first side to said second side to allow gas from said control valve through said body member when connection has been made;
said body member including a seat around said passage on said second side, which is closable by said valve member, to open and close said passage when desired.
Preferably the valve member is movably held between said body member and a second member which connects to said body member.
The body member can be made from a plate having on one side connection means to connect either directly or remotely to said control valve.
Preferably said plate includes support members on said second side extending away therefrom.
The body member can include a peripheral wall around said plate. Alternatively said body member can be generally cup shaped.
The second member can be a solenoid casing which is held by or which holds said body member.
Alternatively the second member can be a tubular member such as a ferrule tube, which is held by or which holds said body member, said tubular member in turn being held by or which holds a solenoid casing.
The second member being held by support members on said body member so as to be kept a predetermined distance away from said seat.
The second member having associated therewith a bias means to bias said valve member towards or away from such seat.
The operator when in use being directly connected to said control valve,
Alternatively the operator when in use is connected to said control valve by means of a tube allowing the operator to be remotely located relative to said control valve.
The body member preferably has a plurality of ports formed between a like number of support members extending away from said body member.
Preferably the valve member is a plunger.